Submarine slope failure due to gas hydrate dissociation: a preliminary quantification

Gas hydrates are icelike compounds composed of water and methane gas in very compact form. There is substantial evidence from case histories that links gas hydrate dissociation to submarine slope failures and other geohazards. Theoretical analyses have also shown that upon dissociation gas hydrates will cause an increase in fluid pressure and a reduction in effective stress and thus result in loss of the soil strength. This paper presents a preliminary quantification of the effects of gas hydrate dissociation through development of a pore-pressure model that was incorporated into one- and two-dimensional slope stability analyses. The ensuing numerical study investigated submarine slope stability through parametric studies and application to two important case histories and found that dissociation of even small amounts of hydrate can have a significant destabilizing effect. Yet whether gas hydrate dissociation can alone cause large-scale slope failures has still to be demonstrated as there are often many destabilizing processes; however, this research highlights the importance of assessing the effects of gas hydrate dissociation on the behaviour of submarine slopes.